The invention refers to a circuit arrangement for the electrical control and/or regulation of the movement of an electrically driven unit, e.g. of an electrically driven adjusting drive in a vehicle. The invention also refers to a method for the electrical control and/or regulation of the movement of an electrically driven unit. The method and the circuit arrangement particularly refer to the recognition of jamming situations with electrically driven adjusting drives in motor vehicles, such as window winders, sunroofs or seat adjustment devices.
There are various regulations and directives that refer to such adjusting drives, for example 74/60/EEC by the European Union, EC21 by the United Nations Economic Commission for Europe (UNECE), FMVSS118 by the National Highway Traffic Safety Administration of the USA etc. All these regulations require limiting the jamming force to a maximum of 100 Newton in the presence of certain operating and test conditions.
From DE 44 42 171 A1, a method is known in which, for the recognition of jamming situations, the performance parameters of the electric motor are continuously picked up at measuring instants that are equidistant in time, and the adjusting force is determined therefrom.
Usually, brush-commutated d.c. motors with two magnetic poles are used in adjusting drives of motor vehicles. Commutation results in so-called current ripples on the motor-current signal, wherein a ripple occurs with each commutation.
In addition, the voltage of the electrical supply system of a motor vehicle also comprises alternating components when certain operating conditions prevail. These alternating components of the motor voltage cause additional alternating components in the motor current.
According to the general state of the art, a continuous signal is low-pass-filtered prior to equidistant-in-time sampling, wherein the limit frequency of the low-pass filter is lower than half of the sampling frequency. According to well-known Shannon's sampling theorem, this is necessary in order to prevent so-called aliasing effects. Usually, the utilized motors comprise between 8 and 12 slots so that 10 current ripples per revolution occur in a 10-slot motor. Thus, an alternating-current signal with a frequency of 10 times the speed superposes on the motor-current signal. Depending on the load and the operating voltage, the speed of the rotor is typically between 10 and 80 revolutions per second. Thus, the alternating components in the motor current caused by commutation are within a frequency range of between 100 and 800 Hz.
Typically, the motor current variations caused by jamming situations are within a frequency range of less than 20 Hz.
Usually, the components caused by commutation are suppressed by means of a low-pass arrangement that also suppresses the higher-frequency components of the alternating components in the motor current caused by ripples in the electrical supply system of the vehicle. For example, it is necessary to select a limit frequency of the low-pass filter of significantly lower than 100 Hz in order to sufficiently damp current ripples at 100 Hz.
In a jamming situation, the adjusting force increases which causes an increase in motor current. As shown in FIG. 2, low-pass filtering causes a delayed increase in filtered current which in the end results in a delayed recognition of jamming situations and thus in increased jamming forces.
Since the alternating components are very big in the presence of certain operating conditions, a very high degree of suppression is usually selected within the frequency range of the disturbing alternating components. This is achieved either by using appropriately low limit frequencies or by using appropriately high filter orders. However, low limit frequencies and high filter orders disadvantageously increase delay times.
Thus, the object of the invention is to provide a method and a circuit arrangement that improve the recognition of jamming situations.